The present disclosure relates to the field of large-scale water treatment, and more particularly to the treatment of aqueous borne waste from municipal, commercial and industrial operations; but is not limited thereto. In my prior issued patents: U.S. Pat. No. 5,762,418, U.S. Pat. No. 6,029,955, U.S. Pat. No. 6,036,357, U.S. Pat. No. 6,322,056, U.S. Pat. No. 6,554,259, U.S. Pat. No. 6,599,426, U.S. Pat. No. 6,926,437, and U.S. Pat. No. 7,083,324, I define apparatus and methods for treating sludge and other materials. The present invention extends this body of knowledge and particularly applies the utilization of the combination of gravity and buoyancy to assist where mixing is required in waste digesters.